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UNITED STATES umane PATENT OFFICE.

FRANCIS W. DUNBAR, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO KELLOGG SWITCHBOARD & SUPPLY COMPANY, A CORIORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed February To all echo-m it may coowcrn:

Be it known that I, FRANCIS IV. Dunn-in, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented new and useful Improvements in Automatic Telephone Systems, of which the following is a specificatiou.

The present invention relates to automatic telephone systems generally and has to do more particularly with systems of the socalled master-switch type, in which the so-callcd selectors and connectors are employed in conjunction with similarly constructcd line selectors" controlled by master-switches. To give a cleaner idea of this type, it may be stated that with one hundred point switches and on a basis of ten per cent trunking, a ten thousand line exchange might be provided with one hundred master-switches, one thousand line selcctors, one thousand first selectors, one thousand second selectors and one thousand connectors; each subscribers line would then be multipled to ten line selectors and ten connectors; and line selectors and first selectors would be united in pairs without multiplying; the wipers of the second selectors would be multipled to bank contacts ot one hundred first selectors, and the wipers of each connector would be multipled to bank contacts of one hundred second selectors. These values, of course, may be departed from, but they serve to indicate fuliv the character of the type of system referred to.

In systems of this type and in other automatic systems heretofore proposed, the construction of the switches employed has been more or less complicated in order to bring about the proper operation of the system.

One of the principal objects of the present invention is to devise a system of the character indicated. in which comparatively simple switch mechanism may be employed in conjunction with ordinary relays to bring about the proper operation of the system. In other words, instead of relying on mechanical movements to bring about certain necessary circuit change, it is sought to provide novel circuits for accomplishing these resu ts with comparatively simple mechanism. The invention contemplates the use of such simplified circuits in connection with three classes of switching 18, 1908. Serial No. 416,607.

mechanisn'i which may be defined as (l) poly-wiper, circular, step-by-step release, switches; 2) poly-wiper, linear, circular or arcuate, spring release switches; and (3) double-motion, or two dimension, arcuate switches with spring release. In the latter class, the movable contacts, or wipers, are associated with a large number of fixed, or nrzsivc, contacts arranged in a bank, and the wipers are first given a movement in one direction, followed by a movement at an angle thereto,the former, or primary, movement bringing the wipers to a desired groupof bank contacts, and the latter, or secondary, movement causing the wipers to engage desired bank contacts in the selected group. These switches are returned to normal through the agency of retractile springs In the switches of the other classes, a wiper and bank contacts perform a function equivalent to the primary movement of the wipers of the two dimension switch, and a second wiper and associated bank contacts perform a r'unctio-n similar to the secondary move ment of the wipers of the two dimension switch. In the case of the first class, the re lease is obtained by continuing the forward motion of each set of wipers until their normal positions are reached; while in the second class, the release, is obtained by the use or retractile springs.

Another object of the invention is to extend this idea of simplification to all commercial adaptation of straight automatic systems so as to include nickel-i11-the-slot service, measured service, party line service, and unlimited service.

Still another object of the invention is to provide a novel arrangement of electrical connections between the switches whereby any calling line may be connected to any second selector, thereby decreasing the chances of being unable to complete a desired conversational circuit.

The invention also includes other features and details which, together with the above, will be more fully understood upon reference to the following detailed description, taken in connection with the accompanyin drawings, and the scope of the invention wil. be pat'ticularly pointed out in the appended claims.

Before considering the drawings, however, it may be noted that in developing the invention along the lines indicated, many features have been devised which are capable of use in other relations than those herein indicated and in the various telephone systems including manual systems and so-called scmiautomatic systems, as well as straight automatic systems.

Referring to the drawings, Fig. 1, which includes parts 1, 2, 3 and t, illustrates diagrammatically a preferred embodiment of telephone system employing switches of the first class and illustrating individual lines, party lines, slot service lines, and meter service mechanism at the. central otlice; Fig. 2, which includes parts 1, 2, 3 and 4, illustrates diagrammatically a modified automatic telephone system employing switches of the second class adapted to secure service similar to that of Fig. 1, but omitting the slot service and meter service equipment; Fig. 3, which includes part 1 and 2, illustrates diagrammatically a second modified automatic telephone system employing switches of the third class and likewise omitting slot service and meter service equipment; Fig. it illustrates a novel method of interconnecting and trunking between switches; Fig. 5 is a top view of a switch of the first class designed for use in the circuits of Fig. 1; Fig. 6 is a central section of the same taken on a plane indicated by the line 6-6 of Fig. 5; Fig. 7 is a top view, similar to Fig. 5, ot a switch of the second class, designed for use in the circuits of Fig. 2; Fig. 8 is a diagram of the wipers and bank H contacts of the primary portion of the switches of the first and second classes; Figs. 9, 10 and 11 are similar diagrams of the secondary portion of said switches; Fig. 12 is a similar top view of a modified switch of the first class provided with meter service mechanism; Fig. 13 is a partial sectional view of the same taken on the line 99 of Fig. 12; Figs. lt, 15 and 16 are elevations of a line selector of the third class of switches designed for use in the circuits of Fig. 3, the selector illustrated being typical of other selectors and the connectors employed in the form of the invention illustrated in said figure; Fig. 17 is a top view of said switch; Fig. 18 is a section plan of a portion of the same taken on a plane indicated by the line 2l2l of Fig. 15; Figs. 19 and 520 are front and side elevations respectively of a master-switch employed in the control of the line selectors; and Fig. 21 is a sectional view of slot mechanism of the type diagrammatically represented in Fig. 1. Throughout these views, like characters refer to like parts.

System of Fir/- signed. for either individual or party line service. In the diagram, party line connections of three other similar substation equipments are indicated at M M M These substations are united to the exchange line limbs P-S which extend, by extension conductors, to the multiple contacts of line selectors Q, and connectors lV, as will be hereinafter more fully explained. Connection is obtained between the subscribers line at the left of the diagram and that. at the right through the agency of a master-switch O, a line selector Q, a first selector U, a second selector V, and a connector lV. Assuming that the selectors and connectors employed are provided with one hundred line bank contacts in the secondary portion of the switch, and assuming that there are ten thousand lines in the exchange arranged on a basis of ten per cent trunking, then, where individual lines are employed, the number of switches (considering the primary and secondary portions of each switch as a single switch) and their multiple arrangement would be that heretofore outlined; namely, one hundred master-switches 0, one thou sand line selectors Q, one thousand first selectors U, one thousand second selectors V, and one thousand connectors \V. The sub scribers lines would be divided into groups (for the initiation of calls) of one hundred lines each and ten line selectors would be assigned to each such group, thus enabling each line to he multipled to the corresponding bank contacts of ten different line selectors. Each group of line selectors would be under the control of one master-switch having a pair, or set, of bank contacts assi ned to each line selector. Each subscribers line would also be multipled to the bank contacts of ten connectors whereby a group of ten connectors become available for estab lishing connections to a group of one lumdred lines. The lines comprising said latter group of one hundred lines may, however, be distributed among a large number, or all. of the groups provided for the initiation of calls.

Now, in case party lines are employed, each such line is multipled to a number of sets of connectors corresponding to the number of selectively signalled substations on the line. Thus in the diagram, the bank contacts of four sets of ten connectors each are represented at W, V. VP and V, corresponding to the tour selectively signalled substations M, M M and M' on the line. From this it will be seen that with a tourparty line, such as illustrated, each line may, if desired, be multipled in the bank contacts of forty connectors. On the other hand, in the case of individual lines as previously pointed out, only the connections of one of these sets would be employed, such as that indicated at V, thus providing but ten multiple connections per line. Of the ten multiple connections between each indivi dual line and the line selectors Q, only one set of such connections is illustrated, but others are indicated by the multiple taps. Similarly, in a party line, the number of multiple connections to the line selectors may be greater than ten. Moreover, it is obvious that in the case of either individual or party lines, the number of line selectors provided for a group of calling lines, or the number of connectors provided for a group of called-for lines, may be increased above ten, as desired. All of this will more fully appear from the following description.

In outline, the connections between the switch contacts are as follows: The movable contacts, or wipers, of each line selector Q are tied to corresponding wipers ot a first selector U, thus providing one thousand direct connections between one thousand line selectors and the one thousand first selectors. The wipers of the second selectors V are connected to the bank contacts of the first selectors U; and since there are in the illustration assumed, one thousand of each of these selectors, the wipers of each second selector are connected to the corresponding bank contacts of one hundred first selectors. Similarly, the wipers of each of the thousand connectors TV are connected to the corresponding bank contacts of one hundred second selectors V. As previously indicated, this apportionment of values, either as to the number of switch points or percentage of trunking in any part of, or throughout, the system, may be varied to suit the exigencies of any particular case.

In the operation of these instrui'nentalities in establishing connection between a substation on the line PS at the left, as substation M, and one located on the line associated with extension conductors at the right, the calling party at substation M first removes his receiver from its hook and, it the line be idle, deposits his token in the slot mechanism and thereby, through the agency of a master-switch 0, sets an idle line selector Q in operation to automatically seek out and establish connection with his line, thus extending the calling line circuit to the first selector U, paired with the actuated line selector The calling party then, by means of his calling mechanism, transmits a number 01 impulses corresponding to the digits of the number of the subscriber wanted. The first series of these impulses operates the connected first selector U so as to cause it to pick out and es tablish connection with an idle second selector V associated with the thousands group to which the called line belongs.

Thus if the number of the calling party be 2000 and some odd, the first set of two 1mpulses will move the wipers of the primary portion of the first selector U teestablish connection with a particular set of wipers of the secondary portion of the switch which will then automatically move over the contacts associated with it until an idle setof contacts is encountered, thereby extending the circuit of the calling party to an idle sen 0nd selector in the second thousands group The second series of impulses will similarly operate the second selector V to pick out and establish connection with an idle connector W associated with the hundreds group to which the called line belongs. The third series of impulses may then be transmitted over the circuit to cause the operation of the primary wipers of the connector W to establish connection with the secondary wipers having access to the contacts of the sub-groups of ten lines containing the called line; and the final series of impulses will cause the selected secondary wipers to move over their bank contacts until they encounter the contacts corresponding to the called-line, thus completing connection between the calling and the called lines.

Each line is provided at the exchange with a line relay LR, which is instrumental in closing, through the master-switch O, a starting circuit for an idle line selector Q. upon the initiation of a call; also with a cut ofi' relay GO, which is used to destroy the normal substation control of the line relay and to otherwise vary the line connections.

T 1e master-switch O, in the present in stance, comprises a pair of wipers 202l co-operat-ing with bank contacts and caused to step over said contacts by motor magnet MM, the complete operation being controlled by relays 2l-25, as hereinafter more fully pointed out.

The line selector Q includes the primary wipers 26, 27, 28, 29, co-operating with primary bank contacts 30, 31, 32, 33 respectively, and a plurality of sets of secondary wipers 3 t, 35, 36, co-operating with secondary bank contacts 37, 38, 39, respectively. The movement of the primary wipers 26, 27, 28, 29 will be brought about by the primary magnet PM controlled by primary relay PR; and the movement. of the secondary wipers, brought in the circuit by the operation of the primary wipers, will be sin'iilarly brought. about by the secondary magnet Sli'l controlled by a secondary relay SR. The release of the switch, which permits the return of all its parts to normal position, is brought about by the release magnet Elli. The line selector is also PIOflClQCl with primary and secondary ctr-normal switches PO and SO which are operated upon the first mo 'ement of the primary wipers and the first movement of the secondary wipers, respectively. This switch may also be provided with a printing or recording mechanism indicated at X, which will be described more fully hereinafter,

The first selector U includes the primary wipers 40, 41, 42, co-operating with the primary bank contacts 43, 1 1, 45, respectively, in response to the operation of the primary magnet PM controlled by the primary rclay PR; and a plurality of sets of secondary wipers L6, 4L7, 4:8 co-operating with bank contacts 49, 50, 51 respectively, and in turn actuated by the secondary magnet SM controlled by the secondary relays SR and SR. The release of the switch parts, which permits their restoration to normal, is brought about through the release magnet RM. This switch is also provided with a primary cit-normal switch PO and a secondary oil-normal switch S0, here as before operated by the first movements of the primary and secondary wipers respectively. The circuit associated with this selector also includes a reversing relay RV for reversing the direction of current supply to the calling line for purposes which will hereinafter more fully appear.

The second selector V is similar in construction and circuit arrangement to the first selector U and comprises primary wipers 52, 53, co-operating with primary bank contacts 55, 56, 57, respectively, and actuated by primary magnet PM and a plurality of sets of secondary wipers 58, 59, (i0, co-operating with secondary bank con tacts 61, 62, 63, and actuated by a secondary magnet SM controlled by the secondary relay SR In this instance, the restoration of the switch parts is accomplished by the release magnet RM and the switch, as before, is provided with primary and secondary off-normal switch contacts, designated P0 and SO respectively.

The connector TV is provided with primary wipers 64, 65, 66, co-operating with primary bank contacts (37, 68, 69 respectively, and actuated by a primary magnet PM and a plurality of sets of secondary wipers 70, 71, 72, co-operating with secondary bank contacts 73, 74, 75, respectively, and actuated by secondary magnet SM. As before, the switch parts are restored to normal by the actuation of a release magnet, designated HM The connector is also provided with primary and secondary oil-normal contacts designated respectively P0 and S0 In addition to these parts, associated circuits are provided with a busy relay BR, a ringing relay RG, a closing relay OR, a tip relay TR, a socalled flip-flop relay FF, and a relay R, all which co-operate in a manner more fully set forth hereinafter.

The equipment at substation H includes the usual switclrhook 76, receiver 77, callbell 7S, transmitter 79, calling mechanism 80, and slot mechanism 81, including a polarized relay 852.

At the exchange, the connections of the subscribers lines to the multiple contacts of the line selectors Q and to the connectors W will be brought about through the agency of a distributing board DB and extension conductors 83, 84, 85, 86, preferably arranged in the manner illustrated.

Opemz i0'n.Having now given a general description of the character of the apparatus diagrammatically illustrated in Fig. 1, it is believed that a further understanding of the invention will be best accomplishcd by entering at once into a description of the operation of the system therein depicted.

Assuming that a party at substation M on the line PS at the left desires to converse with a party at a substation on the line associated with extension conductors S6 at the right, and assuming that the number of the latters telephone is 3333, then the calling party first removes his receiver 7 7 from its hook 76 and places the receiver 77 to his ear to determine whether or not the line is idle. This, of course, will only be necessary in the case of a party line.

The idle indication is obtained from an interrupter 87, acting through an induction coil 88, one of whose windings is included in the local circuit with the interrupter, the other of whose windings is included in the grounded branch leading through the line relay LR. This ground branch may be of low resistance and made common to a number of line relays, as indicated in the drawing. Circuit through the calling party's receiver 77, may be traced from the ground at the induction coil 88, through one winding of said coil, line relay LR, normal contact S9 of cut-01f relay CO, line limb S, closed contact 90 of the substation calling mechanism 80, transmitter 79, switchhook 7G, receiver 77, condenser 91, closed con tact 92 of calling mechanism 80, line limb P, normal contact 93 of cut-oil relay CO, protective resistance 94: to ground through battery B. The inductive action, produced in this secondary circuit by the interrupter 87 in the local circuit, produces a characteristic signal in the receiver 77 of the calling party as an indication to him that the line is idle and that he may proceed to make a call. This he does by depositing his nickel, or token, in the slot mechanism 81. It will be observed that the previous movement of the switch-hook 76, occasioned by the removal of the receiver 77, rocks the armature arm 95 pivoted at 95 against the tension of the return spring 96 far enough to bring the upper end of the arm into a position to hold the token against delivery through either of the outlets of the slot. This movement of the arm 95, however, is not sufficient to cause its lower end to engage contact 97. The de posit of the token, by engaging the insulating piece on the spring contact 98, forces the latter from its normal to its alternate posi- 

